ElasticSearch 实战：查询Sort（查询排序）

在ElasticSearch中，我们可以使用sort参数来对查询结果进行排序。

以下是一些使用ElasticSearch的Java API进行查询排序的示例。

1. 使用单个字段排序

SearchRequest searchRequest = new SearchRequest("index_name");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchAllQuery());
searchSourceBuilder.sort("field_name", SortOrder.ASC);
searchRequest.source(searchSourceBuilder);
 
try {
    SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
    SearchHits searchHits = searchResponse.getHits();
    for (SearchHit hit : searchHits) {
        System.out.println(hit.getSourceAsString());
    }
} catch (IOException e) {
    e.printStackTrace();
}

在这个例子中，我们对"index\_name"索引的所有文档进行查询，并按照"field\_name"字段升序排序。

2. 使用多个字段排序

SearchRequest searchRequest = new SearchRequest("index_name");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchAllQuery());
searchSourceBuilder.sort("field_name1", SortOrder.ASC);
searchSourceBuilder.sort("field_name2", SortOrder.DESC);
searchRequest.source(searchSourceBuilder);
 
try {
    SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
    SearchHits searchHits = searchResponse.getHits();
    for (SearchHit hit : searchHits) {
        System.out.println(hit.getSourceAsString());
    }
} catch (IOException e) {
    e.printStackTrace();
}

在这个例子中，我们对"index\_name"索引的所有文档进行查询，并先按照"field\_name1"字段升序排序，若"field\_name1"字段值相同，则按照"field\_name2"字段降序排序。

3. 使用脚本字段排序

SearchRequest searchRequest = new SearchRequest("index_name");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchAllQuery());
searchSourceBuilder.sort(new ScriptSortBuilder(
    new Script(ScriptType.INLINE, "painless", "_value * doc['field_name'].value", Collections.emptyMap()),
    SortOrder.ASC)
);
searchRequest.source(searchSourceBuilder);
 
try {
    SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
    SearchHits searchHits = searchResponse.getHits();
    for (SearchHit hit : searc